Patent Grant
9207007
The invention generally relates to air-conditioning systems and heat pump systems, especially in cooling mode.
Known methods for optimizing Air conditioning systems involve taking measurements of certain temperatures and pressures of a cooling system and determining if the system needs airflow adjustments or refrigerant added or removed. One significant deficiency to prior art methods is the target temperature split, defined as the target return air dry-bulb temperature minus the target supply air dry-bulb temperature, known look up tables are limited to return air dry-bulb temperatures between 70 and 84 degrees Fahrenheit. For return air dry-bulb temperatures between 60 and 69 degrees Fahrenheit, and return air dry-bulb temperatures between 77 and 84 degrees Fahrenheit, and return air wet-bulb temperatures between 50 and 58 degrees Fahrenheit, the target temperature split is undefined as shown in prior art Table 1. In the upper right corner of Table 1, the target temperature split does not exist since and the return wet-bulb temperature cannot exceed the return dry-bulb temperature and the relative humidity cannot be greater than 100 percent (under atmospheric conditions).
Another significant drawback is the target superheat temperature, defined as the refrigerant suction line temperature minus the refrigerant evaporator saturation temperature, is limited to condenser air dry-bulb temperatures of 55 to 65 degrees Fahrenheit at return air dry-bulb temperature of 55 degrees Fahrenheit and condenser air dry-bulb temperature of 115 degrees Fahrenheit at return air dry-bulb temperature of 69 to 76 degrees Fahrenheit. For condenser air dry-bulb temperatures between 65 and 115 degrees Fahrenheit and return air dry-bulb temperatures between 55 and 69 degrees Fahrenheit the target superheat is undefined as shown in prior art Table 2.
In many hot and dry climates throughout the world air conditioning is required to cool interior spaces to maintain indoor comfort. In hot and dry climates when technicians diagnose target temperature split for air conditioners or heat pumps in cooling mode and the return air dry-bulb temperature is in the undefined region using prior art methods, it is impossible to obtain target temperature split to diagnose proper airflow. In hot and dry climates when technicians diagnose target superheat for air conditioners or heat pumps in cooling mode with Fixed Expansion Valve (FXV) systems and the condenser air dry-bulb temperature and return air wet-bulb temperature are in the undefined region using prior art methods, it is impossible to obtain target temperature split to diagnose proper refrigerant charge.
Undefined target temperature split and undefined target superheat values cause technicians to improperly diagnose proper temperature split and superheat leading to significant performance problems that can cause the following problems: insufficient airflow, insufficient cooling capacity, liquid refrigerant entering the compressor, excessive mechanical vibration and noise, premature failure of the compressor, reduced energy efficiency performance, and increased electricity consumption.
Further, there are no prior art methods to differentiate non-condensables from over-charge, and restrictions from under-charge, and without this knowledge, refrigerant would be incorrectly removed from systems with non-condensables present, and added to systems with restrictions.
Correcting non-condensables saves electricity by removing air and/or water vapor from the system to improve heat transfer from the condenser and reduce system pressure and operational time which reduces electric power usage and prolongs the life of air conditioners. Correcting restrictions saves electricity by increasing the mass flow of refrigerant to the evaporator which increases cooling capacity, reduces operational time and proportionately reduces electric power usage.
Correcting overcharged systems with improper airflow saves electricity by reducing refrigerant pressure and proportionally reducing electric power usage. It also eliminates problems of liquid refrigerant returning to the compressor causing premature failure. Correcting undercharged air conditioners with improper airflow saves electricity by increasing capacity allowing them to run less which extends the life of the compressor. It also prevents overheating of the compressor and premature failure.
The present invention addresses the above and other needs by providing expanded target temperature split and target superheat tables based on laboratory data, and mathematical algorithms for distinguishing non-condensables from refrigerant over-charge, and distinguishing refrigerant restrictions from refrigerant under-charge of a cooling system. Methods are disclosed which receive inputs in the form of data describing the cooling system and measurements made from the cooling system, and which estimates the amount of refrigerant to be removed or added to the cooling system for optimal performance. The methods may apply to Fixed Expansion Valve (FXV) systems and may include making and displaying an estimation of a refrigerant adjustment based upon measurements such as return air wetbulb temperature, condenser air entering temperature, refrigerant superheat vapor line temperature, and refrigerant superheat vapor line pressure. The method may apply to Thermostatic Expansion Valve (TXV) systems and may include making and displaying an estimation of a refrigerant adjustment based upon measurements such as refrigerant subcooling liquid line temperature and refrigerant subcooling liquid line pressure. Methods for calculating target temperature split, target superheat, and target enthalpy to ensure correct setup of a cooling system are disclosed. The methods may include distinguishing non-condensables from refrigerant over-charge and distinguishing refrigerant restrictions from under-charge, and making and displaying an estimation of a refrigerant adjustment or of an airflow adjustment based upon measurements such as entering condenser dry bulb temperature, entering return air wet bulb temperature, entering return air dry bulb temperature and supply air dry bulb temperature. Recommendations may also be based upon evaporator coil temperature splits. In addition, methods for ensuring correct setup of a cooling system are disclosed.
In accordance with one aspect of the invention, there is provided a method for verifying proper refrigerant charge and airflow for split-system and packaged air-conditioning systems and heat pump systems in cooling mode to improve performance and efficiency and maintain these attributes over the effective useful life of the air conditioning system.
In accordance with another aspect of the invention, there is provided a method suitable for determining proper R22 and R410a refrigerant level and airflow across the evaporator coil in air-conditioning systems used to cool residential and commercial buildings.
In accordance with still another aspect of the invention, there are provided empirical tables for expanded target temperature split and target superheat and also includes mathematical methods for distinguishing non-condensable air and water vapor faults from refrigerant over-charge and distinguishing refrigerant restrictions from refrigerant under-charge and provides methods to qualitatively and quantitatively improve diagnostic testing and correction of refrigerant charge and airflow for air conditioners and heat pumps in cooling mode. The prior art methods do not provide expanded tables for target temperature split and superheat and do not compute values to distinguish non-condensable air and water vapor faults from refrigerant over-charge and to distinguish refrigerant restrictions from refrigerant under-charge.
In accordance with yet another aspect of the invention, there are provided empirical expanded tables for expanded target temperature split and target superheat and also includes mathematical methods for diagnosing non condensable air and water vapor faults from refrigerant over-charge and refrigerant restrictions from refrigerant under-charge to make a recommendation for recovering refrigerant to address non-condensables or restrictions or to make a refrigerant adjustment or airflow adjustment to improve energy efficiency. The prior art methods do not compute these values nor do they include recommendations based on these calculated values.
In accordance with another aspect of the invention, there is provided a method for calculating target temperature split to ensure correct airflow to achieve optimal energy efficiency performance of a cooling system. The method may apply to a TXV system or an FXV system and may include making and displaying a prediction of target temperature split based upon measurements such as return air wet-bulb temperature and return air dry-bulb temperature.
In accordance with yet another aspect of the invention there is provided a method disclosed for calculating target superheat temperature and tolerances to ensure correct refrigerant charge to achieve optimal energy efficiency of a cooling system. The method may apply to a FXV system and may include making and displaying an estimation of target superheat based upon measurements such as return air wet-bulb temperature and condenser air dry-bulb temperature.
In accordance with another aspect of the invention, there is provided a method for calculating the Condenser Over Ambient (COA) temperature as a function of outdoor air temperature in combination with superheat and subcooling values to detect the presence of non-condensables versus refrigerant overcharge. The method may apply to a TXV or FXV system.
In accordance with still another aspect of the invention, there is provided a method for calculating the evaporator saturation temperature as a function of outdoor air temperature in combination with superheat and subcooling values to detect the presence of refrigerant restrictions versus refrigerant undercharge. The method may apply to a TXV or FXV system.
The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims:
Corresponding reference characters indicate corresponding components throughout the several views of the drawings.
In the following description, for purposes of clarity and conciseness of the description, not all of the numerous engineering equations used to develop the expanded temperature split and superheat tables are described. The engineering equations shown provide a person of ordinary skill in the art a thorough, enabling disclosure of the present invention. The operation of any of the mathematical algorithms would be understood and apparent to one skilled in the art.
Table 3 provides an illustrative example of an expanded empirical target temperature split look up table according to an embodiment of the invention. The target temperature split is defined as the target return air dry-bulb temperature minus the target supply air dry-bulb temperature, for return air dry-bulb temperatures between 62 and 84 degrees Fahrenheit and return air wet-bulb temperatures between 50 and 76 degrees Fahrenheit. The expanded target temperature split values exclude the upper right corner of Table 1 where the target temperature split does not exist since and the return wet-bulb temperature cannot exceed the return dry-bulb temperature and the relative humidity cannot be greater than 100 percent (under atmospheric conditions).
19.1
18.5
17.9
17.3
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15.2
14.2
13.2
12.2
11.3
19.5
18.8
18.4
17.7
16.7
16.0
15.2
14.1
13.3
12.2
11.4
19.7
19.1
18.7
18.1
17.3
16.7
16.0
15.0
14.2
13.2
12.4
11.5
19.9
19.4
19.0
18.5
17.9
17.4
16.8
15.9
15.1
14.2
13.4
12.6
11.6
20.1
19.7
19.3
18.9
18.5
18.1
17.6
16.8
16.0
15.2
14.4
13.6
12.8
11.7
20.3
20.1
19.7
19.2
18.9
18.7
18.0
17.3
16.6
16.1
15.3
14.5
13.8
12.6
20.5
20.3
20.0
19.6
19.3
19.1
18.5
17.9
17.3
16.8
16.1
15.4
14.7
13.7
20.7
20.5
20.3
20.0
19.7
19.5
19.0
18.5
18.0
17.5
16.9
16.3
15.6
14.8
24.7
25.3
25.2
24.9
25.9
25.8
25.5
25.3
25.1
26.5
26.4
26.1
25.9
25.7
25.4
27.1
27.0
26.7
26.5
26.3
26.0
25.6
27.7
27.6
27.3
27.1
26.9
26.6
26.2
25.7
28.2
28.1
27.8
27.6
27.4
27.1
26.7
26.2
25.7
28.7
28.6
28.3
28.1
27.9
27.6
27.2
26.7
26.2
11.9
13.0
12.2
14.1
13.3
12.5
Table 4 provides an illustrative example of the expanded empirical target superheat look up table according to an embodiment of the invention, defined as the target refrigerant evaporator saturation temperature minus the target refrigerant suction line temperature, for condenser air dry-bulb temperatures between 55 and 115 degrees Fahrenheit (° F.) and return air wet-bulb temperatures between 50 and 76 degrees Fahrenheit. The expanded empirical target temperature split table is based on laboratory measurements of an air conditioning system operated at limiting temperature conditions (e.g., 60 F return dry-bulb, 50 F, 54 F, and 59 F return wet-bulb, 63 F return wet-bulb, and 72 F condenser entering air temperature). The expanded empirical target superheat table is based on laboratory measurements of an air conditioning system operated at limiting temperature conditions (e.g., 80 F return dry-bulb, 57 F return wet-bulb, 63 F return wet-bulb, and 115 F condenser entering air temperature). The 2 F lower limit of target superheat is based on empirical data from laboratory measurements of systems with correct charge and 40% over-charge.
5.2
5.1
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5.3
4.9
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4.6
4.8
5.1
5.4
4.5
4.7
5.0
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4.6
4.9
5.1
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4.5
4.
8
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4.
8
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4.7
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4.6
4.9
5.1
5.4
3.9
4.0
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4.7
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5.3
3.8
3.9
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4.3
4.6
4.8
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5.5
3.7
3.8
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4.6
4.9
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3.5
3.7
3.9
4.0
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4.5
4.8
5.1
5.7
3.4
3.6
3.8
3.9
4.1
4.3
4.6
4.9
5.5
3.3
3.5
3.6
3.8
4.0
4.2
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4.
8
5.3
3.2
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3.5
3.6
3.8
4.0
4.2
4.6
5.1
5.0
3.1
3.2
3.4
3.5
3.7
3.9
4.1
4.4
4.9
4.9
3.0
3.1
3.3
3.3
3.5
3.7
3.9
4.2
4.7
4.7
5.3
2.9
3.0
3.1
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3.5
3.7
4.0
4.5
4.5
5.1
2.8
2.9
3.0
3.1
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3.6
3.8
4.3
4.3
4.9
2.7
2.8
2.9
2.9
3.1
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3.4
3.6
4.1
4.2
4.7
4.8
2.6
2.7
2.8
2.8
2.9
3.1
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3.4
3.9
4.0
4.5
4.6
2.5
2.6
2.6
2.7
2.8
2.9
3.1
3.2
3.7
3.8
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4.4
5.3
2.0
2.5
2.5
2.5
2.6
2.7
2.9
3.1
3.5
3.7
4.1
4.2
5.0
2.0
2.0
2.4
2.4
2.5
2.6
2.7
2.9
3.3
3.5
3.9
4.0
4.8
2.0
2.0
2.0
2.3
2.3
2.4
2.5
2.7
3.1
3.3
3.7
3.8
4.6
5.1
2.0
2.0
2.0
2.0
2.0
2.3
2.4
2.5
2.9
3.2
3.5
3.7
4.4
4.8
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.7
3.0
3.3
3.5
4.1
4.5
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.5
2.8
3.1
3.3
3.9
4.3
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.6
2.9
3.1
3.7
4.0
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.5
2.7
2.9
3.5
3.7
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.5
2.7
3.2
3.4
2.0
2.0
2.0
2.0
2.0
2.1
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2.3
2.3
2.3
2.3
2.5
3.0
3.1
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.8
2.8
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.6
3.4
2.0
2.0
2.0
2.0
2.0
2.1
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2.3
2.3
2.3
2.3
2.3
2.4
3.1
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.4
2.9
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.7
2.0
2.0
2.0
2.0
2.0
2.1
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2.3
2.3
2.3
2.3
2.3
2.3
2.5
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.4
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.4
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.0
2.0
2.0
2.0
2.0
2.1
2.2
2.3
2.3
2.3
2.3
2.3
2.3
2.3
5.0
Laboratory tests of non-condensables for a split system air conditioner were set-up to approximate conditions that would occur if a vacuum were performed correctly on the system during installation. The line set and evaporator cooling coil were flushed with nitrogen at 300 psig and then allowed to equalize to atmospheric pressure. The unit was then sealed and charged to known optimum charge. The estimated amount of nitrogen remaining in the system was 0.3 ounces. The ARI 700 Specification for Fluorocarbon Refrigerant states that maximum allowable levels of contaminants for R22 and R410A are 10 parts per million (ppm) by weight for water, and 1.5% by volume at 75° F. (29.3 C) for air and other non-condensables. This is 200 times less than 0.3 ounces.1 1 ARI Standard 700-2006 Specifications for Fluorocarbon Refrigerants.
Data were taken on the system at the nominal “A” test conditions (95° F. ambient dry bulb and 80° F. dry bulb/67° F. wet-bulb return air). The non-condensables caused the superheat leaving the expansion device to mimic an over-charged diagnosis. Charge was removed until the unit reached proper superheat leaving the evaporator and the “A” test was repeated. Impacts on compressor power were significant for both tests.
Extended tests (A through D standards, plus additional steady state data over a range of ambient conditions) were performed for similar amounts of nitrogen in the system. For these tests, 0.3 oz of nitrogen was added to the system instead of relying on estimates based on the volume of nitrogen filled components. These extended tests were performed with the system using both the Thermostatic Expansion Valve (TXV) and the non-TXV devices.
Table 5 provides laboratory test results for 0.3 oz (˜0.3% of system charge) of non-condensable nitrogen on the unit operating with the TXV. The loss of efficiency is −12.2% for the Energy Efficiency Ratio (EER)*A, −13.4% for EER*B, and −13.4% for Service Energy Efficiency Rating (SEER)*. The non-condensables increased unit power consumption at the “A” test condition by 201 Watts or 6.1%.
Table 6 provides laboratory test results for 0.3 oz (˜0.28% of system charge) of non-condensable nitrogen on the non-TXV unit. The loss of efficiency is −18.2% for the EER*A, −22.5% for the EER*B, and −18.5% for SEER*. The presence of non-condensables increased electric power consumption by 252 W or 7.6% for the EER*A test.
The first trial set of non-condensable were also tested with a charge adjustment to provide correct superheat leaving the evaporator. The efficiency improved by 2% at the “A” test point. The efficiency increase was a result of reduced unit power consumption as cooling capacity was unchanged. The impact of ˜1% non-condensables (Test 501X) was −37.7% for the EER*A test with a power consumption increase of 0.71 kW (22%). Earlier tests with high levels of nitrogen where charge was adjusted to provide correct superheat leaving the evaporator indicates that unit efficiency would improve with the removal of charge. With correct superheat, cooling capacity increased to near its rated value and unit power consumption showed a modest reduction. For the one set of tests where direct comparison could be made, the overall EER*A efficiency improvement is 2% from the charge adjustment.
Test 501X data is for a unit with full refrigerant recovery (i.e., condenser, compressor, and evaporator), and time-based evacuation with vacuum pump containing dirty oil. The time-based evacuation was approximately 8 hours rather than evacuating to 500 microns and checking that vacuum held at 500 to 700 microns for 10 minutes. Similar vacuum procedures (time only without the use of a pressure gauge) are common in field installations. It is likely that all but the newest service vacuum pumps would have contaminated oil. Based on this observation, the presence of some level of non-condensables in newly installed systems should be considered common.
Refrigerant restrictions can be caused by partial orifice freeze-up from moisture (non-condensables), TXV adjusted too far closed, expansion valve defect, metering device restrictions (non-TXV or TXV), plugged inlet screen, foreign material in the orifice, filter drier restrictions, kinked or restricted liquid or suction lines, oil logged refrigerant flooding the compressor, wax buildup in valve from wrong oil in system, flux, or sludge from byproducts of compressor burnout. If the restriction is at the metering device, then frost or ice will develop at this location. If the restriction is at the liquid line or filter drier, then the liquid line temperature will be colder than ambient with an inlet minus outlet temperature difference of approximately 5° F. or greater.
Correcting restrictions requires recovery of refrigerant, removal of restriction, installation of filter drier, nitrogen purge and leak test, and proper system evacuation. A new filter drier must be installed on all new systems and anytime the system is opened. Filter driers remove moisture, acid, contaminants (scale, solder particles, dirt), hydrochloric, hydrofluoric, and various organic acids, varnish, and sludge. If pressure slowly rises to 1500 microns, the system has air or moisture. If pressure rapidly rises to atmospheric pressure system has leaks. If the vacuum holds at or slightly above 500 microns after 5 to 20 minutes, then the vacuum is complete, and the system can be recharged with clean refrigerant. Restrictions can be avoided with proper installation, evacuation, and maintenance, procedures.
At present there is no database on the relative severity of refrigerant restrictions. Restrictions were generated in the laboratory by adding a valve in the liquid line before the expansion valve. The valve position was adjusted until the evaporator saturation temperature was reduced by 14° F. to 18° F. and the overall system pressure ratio (ratio of pressure readings across the service ports) increased by 15% to 20%. These changes in system operating conditions are equivalent to a system under-charge of between 10 and 15% of full charge. As such, these tests would not be sufficiently severe as to generate cooling coil icing at ambient temperatures that would require significant cooling system operation. The impact of the restriction used in the laboratory tests would likely go undetected by a system's owner or typical service technician.
Table 7 provides laboratory test results for refrigerant restrictions on the non-TXV unit. The efficiency impact is −29.7% for the EER*A test, −45.4% for the EER*B test, and −35.4% for the SEER* test. Unit power decreased by 100 Watts, or 3%. Trends of changes in unit performance mirror those for under-charged units. That is, efficiency decreases even though power consumption decreases since the fall off in capacity is more rapid than the decrease in unit power consumption.
Table 8 provides laboratory tests for refrigerant restrictions on the TXV unit. The impact is −36.1% for the EER*A test, −54.9% for the EER*B test, and −59% for the SEER* test.
The metering device 6 may control the rate at which the refrigerant enters the evaporator coil 10 and may also create a pressure drop. This allows the refrigerant to expand from a small diameter tube to a larger one. Fan 7 blows an air flow 8 through the evaporator coil and the refrigerant absorbs heat from the air flow 8 cooling the air flow 8 and the refrigerant evaporates back to vapor 9. The refrigerant vapor 9 returns to the compressor 1 to start cycle over again.
Cooling system measurements may be used to lookup the target superheat using the expanded superheat table, and diagnose proper refrigerant charge and recommend a weight of refrigerant to add or remove from the air conditioning system, to achieve a balance of saturated refrigerant vapor in the evaporator coil and condenser coil to provide optimal cooling capacity and/or energy efficiency. Examples of suitable processors for evaluating the measurements include: a Personal Digital Assistant Expert-system Software (PDAES) or Telephony Expert-system Software (TES), deploying Interactive Voice Response (IVR) technologies; 3) personal computer (PC) software; and 4) internet database software, accessed via a web-based browser interface.
For air conditioners equipped with FXV devices 6, a factory refrigerant charge, and the following measurements may be evaluated: Return wet-bulb and return air dry-bulb temperature measured at the evaporator coil (near 7,
For air conditioners equipped with TXV devices, the factory refrigerant charge and the following measurements may be evaluated: Return wet-bulb and return air dry-bulb temperature measured at the evaporator coil (near 7,
For either FXV or TXV systems the following measurements may be evaluated: return (entering) wet-bulb and dry-bulb temperatures are measured at (7) at the inside coil (left) and supply dry-bulb is measured at (8). These measurements are used to lookup the target temperature split and diagnose proper airflow across the evaporator coil and recommend corrective steps to improve airflow or to check and correct refrigerant charge to provide optimal cooling capacity and energy efficiency. The airflow methodology is based on standard methods known to persons of ordinary skill in the arts.
The expanded temperature split table is used to evaluate the return and supply air enthalpy split used to determine the energy efficiency improvement based on Refrigerant Charge and Airflow (RCA) improvements. The temperature split is defined in Equation 1.
TS=tr−ts Eq.1.
Where,
For either FXV or TXV systems the following measurements are evaluated: Return wet-bulb and return air dry-bulb temperature measured at the evaporator coil (near 7,
The expanded superheat table is used to evaluate refrigerant charge. The actual superheat is defined in Equation 2.
SHa=Tsuction−Test Eq. 2.
Where,
Prior art assumes the delta temperature split must be within a tolerance of plus (+) or minus (−) 3 F.
Expanded empirical target superheat values are provided in Table 3. Delta Superheat (DSH) is calculated using Equation 3.
DSH=SHa−SHt Eq. 3.
Where, DSH=delta superheat temperature difference between actual and target superheat (° F.),
Prior art assumes the delta superheat must be within a tolerance of plus (+) or minus (−) 5 F (i.e., −5° F.≦DSH≦5° F.).
If target superheat (SHt) is less than or equal to 7° F. and greater than or equal to 2° F. (lower limit), then to avoid overcharging the delta superheat tolerance is defined in Equation 4.
Delta Superheat Tolerance=2° F.−SHt≦DSH≦12° F.−SHt Eq. 4.
Where expanded empirical target superheat table values are provided in Table 4.
Non-condensable diagnostics are evaluated based on a series of tests over a wide range of air temperatures entering the condensing unit. Tests were performed with 0.3 ounces nitrogen contamination (approximately 0.3% of unit charge by weight). The standard diagnostic for the presence of non-condensables is the value of condenser saturation temperature minus the ambient temperature of the air entering the condenser coil. Prior art refers to this as a Condenser saturation Over Ambient (COA) test. Values of the COA for the unit loaded with 0.3 oz of nitrogen are shown in
It seems likely that the second observation would hold for most modern higher efficiency single-speed spit-system cooling systems. The nominal design COA for the properly charged test unit at the “A” test point was 15° F.±0.5° F. This was independent of the expansion device and whether or not the unit was tested assuming hot attic conditions or standard room temperature conditions surrounding the evaporator section. Non-condensables increased the condenser saturation temperature by an additional 11 to 13° F., depending on the expansion device. Given this, the prior art nominal COA of 30° F. is not applicable to all units. Older, less efficient units typically had smaller, less efficient condenser coils which would have generated a higher design COA value—say 20° F. instead of the test unit's 15° F.—when properly installed. For these units a 30° F. COA diagnostic value could be commensurate with a design COA of 20° F. plus the additional 11 to 13° F. increase associated with the presence of a non-condensable.
Diagnostics tests were developed by fitting a second degree polynomial to the condenser saturation data from the two data sets (TXV and non-TXV). This data was used along with data taken on the same unit in an over-charged condition and with a blocked condenser coil to develop diagnostic algorithms. The data for the over-charged condition and blocked condenser coil were included in the effort as these two faults have similar diagnostic characteristics. The resulting algorithms are described as follows. The algorithms include an offset to adjust for condenser heat exchanger surface area as a function of SEER rating.
Non-TXV Algorithm
If the SEER is greater than or equal to 10 and less than 13, then Equation 5 is used to evaluate the initial test measurement of the condenser saturation temperature minus condenser entering air temperature. Equation 6 is used to evaluate the final test measurement of the condenser saturation temperature minus condenser entering air temperature. Equation 7 is used to evaluate the actual subcooling and delta superheat values. Equation 8 is used to evaluate pass and/or fail criteria based on Equations 5 through 7 to determine if non condensables are present.
T1coa=IF(COA>[0.0004*(OAT^2)+0.8102*(OAT)+T1offset−(OAT)]),“FAIL”,“PASS”) Eq.5
Where,
The result of applying the algorithm to the additional laboratory test data that includes over-charged conditions and blocked condenser coil is shown in Tables 9 and 10. The Column labeled “T4nc” indicates “NC” when a non-condensable is present and “PASS” when not. Algorithms correctly identified the non-condensable condition for units with 0.3% or 1% nitrogen in the system, but not for all other tests including those with over-charge or condenser coil blockage as shown in Table 10. For the +40% charge test (Run 183b) and 80% condenser coil blockage (Run 190-2) the COA is sufficient to produce a “FAIL” for Tests T1coa and T2coa. The T3asc,dsh test is “PASS”, providing the correct overall diagnostic result.
Finally, the logic equations are applied to laboratory test data shown in Table 11. The baseline run 189 has no non-condensables. Runs 197 and 198 contain an estimated 0.3% by weight of nitrogen (weight estimated, not weighed in as for tests 501-505). Run 198 has 5.4% charge removed to increase delta superheat (DSH) from 1.7° F. to 12.9° F. per the current CEC refrigerant charge protocol. For Runs 197 and 198 (with or without the charge removal) the logic equations indicate the presence of non-condensables (NC).
The following algorithms described in Equations 9 through 12 are developed from test data in which the TXV was used as the control device. The algorithms include an offset to adjust for condenser heat exchanger surface area as a function of SEER rating. Equation 9 is used to evaluate the initial test measurement of the condenser saturation temperature minus condenser entering air temperature. Equation 10 is used to evaluate the final test measurement of the condenser saturation temperature minus condenser entering air temperature. Equation 11 is used to evaluate the actual subcooling and delta superheat values. Equation 12 is used to evaluate pass and/or fail criteria based on Equations 9 through 11 to determine if non condensables are present.
TXV Algorithm
T5coa=IF(COA>[0.0003*(OAT^2)+0.8672*(OAT)+T5offset−(OAT)]),“FAIL”,“PASS”) Eq. 9
Where,
The logic equations were applied to the laboratory test data shown in Tables 12 and 13. As the data in the tables indicate, the algorithm was able to identify a non-condensable and differentiate that condition from over-charge faults.
Refrigerant restriction diagnostics are evaluated based on a series of tests conducted with a restriction introduced by partially shutting a valve just before the expansion device. The evaporator saturation temperatures with a restriction versus condenser entering air temperatures are shown in
Diagnostics tests were developed by fitting a second degree polynomial to the evaporator saturation temperature data from the non-TXV data. These data were used along with data taken on the same unit for under-charged conditions to develop the diagnostic algorithms. The data for the under-charged conditions are included as these two faults have similar diagnostic characteristics. The non-TXV algorithms are described in Equations 13 through 15. The algorithms include an offset to adjust for evaporator heat exchanger surface area as a function of SEER rating. Equation 13 is used to evaluate the initial and final test measurement of the evaporator saturation temperature. Equation 14 is used to evaluate the actual subcooling and delta superheat values. Equation 15 is used to evaluate pass and/or fail criteria based on Equations 13 and 14 to determine if refrigerant restrictions are present.
Non-TXV Algorithm
T1est=IF(EST<[−0.0029*(OAT^2)+1.1006*(OAT)−T7offset]),“FAIL”,“PASS”) Eq.13
Where,
It seems likely that the second observation would hold for most modern higher efficiency single-speed spit-system cooling systems. The nominal design EST for the properly charged test unit at the “A” test point was 45° F.±5° F. This was independent of the expansion device and whether or not the unit was tested assuming hot attic conditions or standard room temperature conditions surrounding the evaporator section. Restrictions lowered the EST by an additional 14 to 18° F., depending on the expansion device in use. Given this, the prior art nominal EST restriction threshold of 28° F. cannot be used to properly diagnose refrigerant restrictions.
The logic equations are applied to the laboratory test data shown in Tables 14 and 15. The Column labeled “T3rr” indicates “RR” for the runs with restrictions and “PASS” for all other tests including the non-TXV laboratory tests for low airflow and under-charge shown in Table 15. For the −40% charge test (Run 188-2) the EST generates a “FAIL” for T1est, but the T3asc,dsh is “PASS” indicating that the logic equations and algorithms can differentiate restrictions from under-charge for the non-TXV equipped air conditioner.
entering factory charge (ounces);
entering return wetbulb, condenser entering air and Required Subcooling (RSC) (° F.);
entering liquid and vapor line temperature (° F.);
entering liquid and vapor line pressure (psig);
calculating Condenser Saturation Temperature (CST), Evaporator Saturation Temperature (EST) and Required Superheat (RSH) (° F.);
calculating Actual Subcooling (ASC) and Actual Superheat Temperature (ASH) (° F.);
calculating Delta Subcooling (DSC)=ASC−RSC;
calculating Delta Superheat (DSH)=ASH−RSH Temperature (° F.)
if:
EST>[−0.0029*(OAT^2)+1.1006*(OAT)−T7offset]; and
then,
otherwise:
end.
Diagnostics tests were developed by fitting a second degree polynomial to the evaporator saturation temperature data from the TXV test data. This data were used along with data taken on the same unit in an under-charged condition to develop the diagnostic algorithms. The data for the under-charged conditions are included as these two faults have similar diagnostic characteristics. Restriction diagnostic algorithms for the air conditioning system controlled by a TXV are developed in a similar manner and are shown in equations 16-18. The algorithms include an offset to adjust for evaporator heat exchanger surface area as a function of SEER rating. Equation 16 is used to evaluate the initial and final test measurement of the evaporator saturation temperature. Equation 17 is used to evaluate the actual subcooling and delta superheat values. Equation 18 is used to evaluate pass and/or fail criteria based on Equations 16 and 17 to determine if refrigerant restrictions are present.
TXV Algorithm
T4est=IF(EST<[−0.0017*(OAT^2)+0.855*(OAT)−T8offset]),“FAIL”,“PASS”) Eq.16
Where,
The TXV diagnostic algorithms were applied to the laboratory test data as shown in Tables 16 and 17. For the −40% charge test (Run 52, Table 18) the EST generated a “FAIL” for T4est, but the T5asc,dsh is “PASS” indicating that the logic equations and algorithms can differentiate restrictions from under-charge for the TXV equipped air conditioner.
entering factory charge (ounces);
entering return wetbulb, condenser entering air and Required Subcooling (RSC) (° F.);
entering liquid and vapor line temperature (° F.);
entering liquid and vapor line pressure (psig);
calculating Condenser Saturation Temperature (CST), Evaporator Saturation Temperature (EST) and Required Superheat (RSH) (° F.);
calculating Actual Subcooling (ASC) and Actual Superheat Temperature (ASH) (° F.);
calculating Delta Subcooling (DSC)=ASC−RSC;
calculating Delta Superheat (DSH)=ASH−RSH Temperature (° F.);
if:
initial EST>[−0.0017*(OAT^2)+0.855*(OAT)−T8offset]; and
then,
otherwise:
end.
The present application claims the priority of U.S. Provisional Patent Application Ser. No. 61/248,728 filed Oct. 5, 2009 and U.S. Provisional Patent Application Ser. No. 61/256,993 filed Nov. 1, 2009, and is a Continuation In Part of U.S. patent application Ser. No. 12/896,727 filed Oct. 1, 2010, which applications are incorporated in their entirety herein by reference.
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| Number | Date | Country | |
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| Child | 13748933 | US |
